The present invention relates to liquid flow measurement systems; more particularly, the invention relates to a flow measurement system for use in hazardous environments, to isolate electrical measurement components from volatile liquids and vapors.
There is an increasing need in industrial applications for maintaining a strict measurement and control over the use of volatile liquid substances, e.g., paint, cleaning solvents, and multiple-component coating materials. The increasing costs of these materials is one factor which dictates strict measurement and control, but the increasing pressures for environmental protection is an equally strong factor. Wherever coating materials are used in industry there is a strong cost consideration for monitoring material flow and coating thicknesses, and for measuring the flow volume of such materials in the distribution system within an industrial plant. Environmental and safety considerations frequently require that coating materials be collected into an environmentally secure space, and that they be distributed from this location into the various coating application positions which exist in the plant facility. It is not unusual for coating materials to be shipped to industrial plant facilities in large barrels or drums, for delivery into a single sealed room within the facility, and then to be pumped through specialized plumbing arrangements to the distribution points within the plant. Since these materials are associated with volatile solvents and vapors, it is important that the distribution room be kept free from electrical equipment of all types, to reduce the likelihood of spark generation which might ignite the materials. As a result, the pumping equipment which is utilized for distributing these materials is frequently air-driven equipment, and the electrical compressors and other electrical equipment which provides the power for this machinery is physically separated from the distribution room to the extent such separation is practical.
In recent years, plural component coating systems have become popular, because the quality of the coating finish leads to improved product value. In a plural component system a base material and a catalyst material are initially separately contained, and the materials are mixed at the time of application to create a coating material which becomes activated and stabilized upon exposure to air. In such systems, it is important that the mixing be accomplished either close to the point of application, or if mixed in the distribution room, that the materials be isolated from exposure to air. The metering of the flow rates of these materials must be carefully monitored, so as to enable a precise proportioning of the respective materials.
There is therefore a need for a flow rate metering system which is safe in a hazardous area and which thereby eliminates the need for placement of electrical components in the vicinity of volatile environments. There is also a need for a flow rate metering system which may be positioned in a voltatile environment, but which may be remotely controlled and activated for the protection of operating personnel. There is also a need for a flow rate measuring system which is capable of satisfactory operation over a wide range of temperatures, and in atmospheres which may be hostile to human accessibility.